@wc_sumpton
Ramon got me to thinking and I tried to alter how my Marines work. The way they're supposed to work is they are A1 D2 unit that gets boosted to A3 when a Artillery is present.
Artillery also boosts Infantry and a pile of other units +1 on the attack.
I had the Marine at A2 and get boosted +1 on the attack with all the other units in the same supportAttachment. But then you have to switch to a MarineA1 unit that only attacks at 1 when no Arty present.
So i made a separate supportAttachment for the jarhead and gave him +2 on the attack when paired with the Arty as he is now just a A1 otherwise.
I gave it the same "bonusType" name as the one that supports the Infantry. When I attack with 1 Inf and 1 Marine and 1 Arty, the Arty gives +2 to the Marine and +1 to the Inf.
We want it to just give +2 to the jarhead and no bonus to the Inf. Is that possible ? It seems I tried when initially doing it but couldn't get it to work, hence the two different types of Marines.
I thought the same bonusType name meant the Arty would only support 1 unit but then which unit was a bit of a problem too but you did say something about which order their listed in gets the support.
I have to dig that one up but anyway, I think I already tried this and there was no solution but ... I'll ask again anyways 
